Messages in this thread | | | Date | Tue, 24 Jun 2008 17:03:35 -0500 | From | Jack Steiner <> | Subject | Re: [bug] Re: [PATCH] - Fix stack overflow for large values of MAX_APICS |
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On Tue, Jun 24, 2008 at 12:24:01PM +0200, Ingo Molnar wrote: > > * Ingo Molnar <mingo@elte.hu> wrote: > > > * Jack Steiner <steiner@sgi.com> wrote: > > > > > physid_mask_of_physid() causes a huge stack (12k) to be created if > > > the number of APICS is large. Replace physid_mask_of_physid() with a > > > new function that does not create large stacks. This is a problem > > > only on large x86_64 systems. > > > > this indeed fixes the crash i reported here: > > > > http://lkml.org/lkml/2008/6/19/98 > > > > so i've added both this and the MAXAPICS patch to tip/x86/uv, and will > > test it some more. Lets hope it goes all well this time :-) > > -tip auto-testing found a new boot failure on x86 which happens if > NR_CPUS is changed from 8 to 4096. The hang goes like this: >
Still looking but here is what I have found so far.
The most obvious change was to revert the patch that changed MAX_APICS to 32k. With this patch reverted, the system still hangs at the same spot.
I noticed that the hang is random. It usually occurs at acpi_event_init() but sometimes it hangs at a different place.
I also observed that the hang does not always occur. The system will boot to the point of mounting /root, then panics because the mount fails. I expect that this is a different failure due to missing drivers. I'll chase that down later.
I added trace code & isolated the hang to a call to synchronize_rcu(). Usually from netlink_change_ngroups().
If I boot with "maxcpus=1, it never hangs (obviously) but always fails to mount /root.
Next I changed NR_CPUS to 128. I still see random hangs at the call to acpi_event_init().
I'll chase this more tomorrow. Has anyone else seen any failures that might be related???
> Linux version 2.6.26-rc7-tip (mingo@dione) (gcc version 4.2.3) #10233 SMP > Tue Jun 24 12:13:46 CEST 2008 > [...] > initcall init_mnt_writers+0x0/0x8c returned 0 after 0 msecs > calling eventpoll_init+0x0/0x9a > initcall eventpoll_init+0x0/0x9a returned 0 after 0 msecs > calling anon_inode_init+0x0/0x11a > initcall anon_inode_init+0x0/0x11a returned 0 after 0 msecs > calling pcie_aspm_init+0x0/0x27 > initcall pcie_aspm_init+0x0/0x27 returned 0 after 0 msecs > calling acpi_event_init+0x0/0x57 > [... hard hang ...] > > on a good bootup, it would continue like this: > > initcall acpi_event_init+0x0/0x57 returned 0 after 38 msecs > calling pnp_system_init+0x0/0x17 > [...] > > the config, full bootlog and reproducer bzImage is at: > > http://redhat.com/~mingo/misc/config-Tue_Jun_24_07_44_17_CEST_2008.bad > http://redhat.com/~mingo/misc/log-Tue_Jun_24_07_44_17_CEST_2008.bad > http://redhat.com/~mingo/misc/bzImage-Tue_Jun_24_07_44_17_CEST_2008.bad > > changing CONFIG_NR_CPUS from 4096 to 8 causes the system to boot up > fine. > > Ingo
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